Greatest Shoal on Earth (2022)

I recently missed an article about South Africa’s massive “Sardine Run” published in Fishing Industry News South Africa in their October Issue.. I can’t believe that I did so, as sardines (pilchards) is, after all, the resource I cut my teeth on, when I decided that to be an effective skipper, I needed to study a bit of fisheries science. As you well know, and as I have been reminded most of my article writing life, I am not a scientist! However science and scientists are so important in this technologically advanced world today that I seldom like to criticise them. Nevertheless, when such a misleading article under the banner of science appears, which I can only believe has not been peer reviewed, I feel I must put the record straight. Having fished as a skipper of a purse seiner from southern Angola right around to Struisbaai on our south coast, and been involved with pilchard landings on our east coast right up to Durban, I believe my views should have some validity. Nobody must mess with our KZN sardine run, though naming it “The Greatest Shoal ….. may just be a bit of exaggeration!

The very first point, over which I find myself at odds with the authors, is their claim that the “riddle” of the East coast migration, is solved by their determining it is purely a (mistaken) event by Nature best described as an (unfortunate) “Ecological Trap.” In my eyes, the power of any single All Powerful God we choose to believe in as Christians, Moslems, or any other faith with a similar belief, must surely be synonymous with the “Power” of Nature. Then, it is surely at the least “cheeky,” and at the most “heretical,” to suggest that Nature (God) might make such a mistake. Certainly, I have never heard of any similar instance blamed on Nature, without the cause been traced back to imperfect mankind’s involvement originally. Since the odds are strong that this migration has occurred for hundreds, and probably thousands of years naturally, this is clearly not the case here!

I am not sure if the photograph that accompanied the article, was added by FINSA, or was part of the original document. Anyhow it is most appropriate in view of what I have to say! The authors suggest that the sardines that arrive on the South Coast are always “Emaciated” and in very poor condition. In fact they are in Prime condition, with the shoals, as is to be expected, numbering more females than males. Almost without exception the females are in a pre-spawning state. At the end of the run, those shoals that return back south inshore, with some still netted, have the females in the condition one expects after spawning is completed, though describing them as emaciated is going too far! Far fewer shoals are seen travelling southwards inshore, and we have always presumed that after spawning is completed, they mostly proceed to deeper water, where the permanently south flowing Mozambique/Agulhas current is normally always in the ascendancy. I am reminded that, when inshore waters are warmer, they do not carry the same plankton levels as the cooler waters. In fact in some instances, when the inshore cooler current is sometimes invaded by a gyre from the offshore warmer surface current, some of the warmer surface water species, like scads and redeye, mix with the sardine shoals.

I equivocally believe that, as has always been accepted, the run is wholly and only a spawning migration. This is borne out by the fact that all the females are full of spawn, and, as detailed by Alan Connell’s valuable research into the planktonic content of the offshore marine waters of KwaZulu-Natal, clearly demonstrated this. He wrote that during the winter months sardine eggs dominate the inshore waters, even when no visible run was observed. In addition, I am told that, when the shoals gather to start their northerly spawning migration, they are well offshore in the cooler waters of the Eastern Cape. In most instances they probably only move inshore towards the end of the wild Coast and the start of the South coast. This leads one to the conclusion, when you remember that there is the occasional year when the sardine run has not occurred inshore, that they are perfectly capable of continuing their migration further out to sea. After all, one is aware that sardines can stand the increased water pressure down to at least 40 m and more, and such shoals are often encountered during the winter by bottom trawlers 15 km and more from the coastline. As the water temperature of every extra fathom from the surface decreases, it is not unusual to find at 300 m depth that it has dropped as low as 12°C. They do have tails, and are very strong swimmers, so can obviously swim against the current, if they have to.

We then come to the question of differing populations. The article seems to argue with itself in that respect. Nobody would argue that they all belong to the same species, Sardinops ocellata. I know nothing about genomic analysis, but do, to a degree, understand the importance of DNA differences in establishing possible differing populations of the same species, and the limit of their locations. It is my opinion, for what it is worth not been a scientist, that there are at least three distinct populations of Sardinops ocellata (pilchard/sardine), between southern Angola and the Eastern Cape. The first extends from southern Angola to the Orange River mouth, the second extends from Lambert’s Bay to Gansbaai, and the third from the Agulhas Banks to Port Elizabeth. In addition to this, there may, at times of plenty, be two satellite populations formed, one from Hollams Bird Island in Namibia to Port Nolloth, and another in the Cape St Francis to Port Elizabeth area. Scientific opinion in this regard has varied a lot over the last 50 or so years. This unfortunately results in my fearing that their current illustration may be a little inclined towards “a fit for convenience” tendency, if I understand it correctly.

Best regards, Jack Walsh.

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